I have read that SA02>=95% is considered normal/healthy, 95%>SA02>=91%
is moderate risk, and 91%>SA02 is a severe/critical risk, where SA02
is the arterial blood oxygen saturation level.

Assuming a typical patient (e.g. typical Hb levels and blood volume,
etc.), what SA02 level would represent an immediate risk of death or
brain cell death?

I acknowlege this is for information purposes only.

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Request for Question Clarification by omnivorous-ga on 25 Nov 2003 05:05 PST

Spurious --

I'm not posting this as an answer, as it appears that you're seeking
the medical evaluation points.  However, the information below comes
from a file that I've had on the desk re: hypoxia.

In a a 1996 brief on building a high-altitude observatory, two scientists from 
the National Radio Astronomical Observatory and the UCSD (San Diego)
School of Medicine put together a complete brief on medical conditions
for a high-altitude observatory.  (NRAO just broke ground a 2 weeks
ago on the observatory.)

The 20-page article has a chart describing blood oxygen saturation
levels and gives a description of the impairment:
National Radio Astronomical Observatory
"Medical and Physiological Considerations for a High-Altitude MMA
Site" (Oct. 10, 1996)
http://www.alma.nrao.edu/memos/html-memos/alma162/memo162.html

The chart describes O2 saturation levels this way:
85-95%: zone of minimal sensory impairment
75-85%: zone of minimal mental impairment
65-75%: zone of incrasing sensory & mental decrement
55-65%: zone of potential collapse

They also note that "different levels of impairment are very
approximate and vary between individuals," something that anyone who's
done a high-altitude chamber test can attest because you'll see very
different reactions among the participants.

If this is sufficient, I'll post it as an answer.  If you're seeking
MEDICAL standards for releasing patients from the emergency room, etc.
then you'lll want to clarify this question.

Best regards,

Omnivorous-GA

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Clarification of Question by spurious-ga on 25 Nov 2003 19:43 PST

Yes, thanks.  That'll do as an answer.

Spurious --

A Google search on this topic should include the term "hypoxia," since
that's the term for reduced oxygen in the body.  However, since
ecologists use the same term for water that's had oxygen reduced from
algae blooms and other problems, you may wish to use a compound search
with one of the 4 types of hypoxia or another term:
hypoxia + anemic + hypoxic
hypoxia + flying

Here's a site that describes types of hypoxia:
Freedictionary.com
"Hypoxia" 
http://www.thefreedictionary.com/hypoxia

Portable pulse oximeters are relatively new devices, becoming
inexpensive and widely available in the last 5 years.  Consequently,
much of the literature underestimates the impact of altitude on blood
oxygen saturation levels.  It is not unusual for a healthy person
living at sea level to drop below 90% O2 saturations at altitudes as
low as 6,000'.  They'll experience the hypoxia as shortness of breath
during exercise and fatigue after several hours.

An interesting web link is this one includes information from
skydivers, including the pre-flight briefing for parachute jumpers:
"Koyn on Hypoxia"
http://www.afn.org/skydive/sta/hypoxia.html

Also, Scientific American did an October, 1992 article titled
"Mountain Sickness" that's pretty interesting.  Though not available
for free on the Internet, your library may have access to it through
an online service such as  Proquest Magazines or Infotrac.  It
includes a history of altitude sickness and notes that "researchers
have shown that every 1,000-foot increase in altitude reduces maximum
work capacity by 3 percent."

Best regards,

Omnivorous-GA

Thanks for the great answer, omnivorous-ga

NO A MEDICAL OPINION  Always consult a qualified expert before risking life!

From personal experience...
I have had the experience of being woken up in ICU by a nurse saying
"Your Oxygen level is 41% - wake up"  but the rest is quite fuzzy.....

Due to a variety of cadiopulmonary problems I have a typical sitting
still rate af about 85-90% without supplying O2, but have been warned
it is critical.

I Do feel it when it happens, leaves me groggy, but it also badly
influenses the ability to realize any problem or axt on it, a bit like
being slightly drunk, but no high, slurred speech, etc

See a doctor!

Thanks for your helpful comment, bobthedispatcher-ga